Zeldovich pancakes at redshift zero: the equilibration state and phase space properties

TL;DR

This paper investigates Zeldovich pancakes in cosmological simulations, demonstrating their one-dimensional collapse, analyzing their phase space properties, and deriving their velocity distribution functions to support their use in galaxy cluster mass estimation.

Contribution

It provides a detailed analysis of Zeldovich pancakes' equilibration and phase space properties, including an analytical derivation of their velocity distribution functions.

Findings

Pancakes are confirmed to be only one-dimensionally collapsed structures.

Density profiles of pancakes match theoretical models reasonably well.

Derived velocity distribution functions agree with simulation data.

Abstract

One of the components of the cosmic web are sheets, which are commonly referred to as Zeldovich pancakes. These are structures which have only collapsed along one dimension, as opposed to filaments or galaxies and cluster, which have collapsed along two or three dimensions. These pancakes have recently received renewed interest, since they have been shown to be useful tools for an independent method to determine galaxy cluster masses. We consider sheet-like structures resulting from cosmological simulations, which were previously used to establish the cluster mass determination method, and we show through their level of equilibration, that these structures have indeed only collapsed along the one dimension. We also extract the density profiles of these pancake, which agrees acceptably well with theoretical expectations. We derive the observable velocity distribution function (VDF) analytically by generalizing the Eddington method to one dimension, and we compare with the distribution function from the numerical simulation.